Oxidation of acrolein to acrylic acid



Patented Feb. 8, 1944 zoom OXIDATION OF Am 1'0 acnmc ACID Hanna PeterStandinger, Ewell, and KarllleinrlohWalterTuerci. ol'sto The rial. No.411,758. In Great 3 Claims.

This invention is for improvements in or relatin: to the oxidation oracrolein to acrylic acid.

Several processes tor oxidisins acrolein to acrylic acid have beendescribed in the literature. but all these processes have suffered fromthe fact that the oxidation, as hitherto practised, has been slow andpolymerisation of both the aclolein and the acrylic acid produced by theprocess takes place at a rapid rate. This polymerisation is thought tobe due either to the prolonged action or the oxygen itself, or moreprobably to the "action or per compounds formed as intermediatecompounds during the reaction.

According to the present invention, the oxidation or acrolein is carriedout by reaction with molecular ween. that is oxygen itself, or gasescontaining omen. in the presence oi the acidic compounds or vanadiumsuch as vanadic acid. The catalyst is preferably Ireshly prepared fromthe corresponding salts by hydrolysis or by the action 01 acids.

The use of. vanadic acid as catalyst not only considerably reduces thereaction time, but also permitstheuseotlowertempcraturesthanhas beenpossible hitherto with a consequentdiminutioninthetendencytopolymerisation. Tiietemperature shouldpreferably not be allowed to exceed 45 C. during the oxidation andgenerally speakins a temperature or 2040' C. will be ioimd to give mostsatistactory results. Though the solution contains a considerable amount01 peraoidandperoxidethemonomericacrylicacidis obtainedinveryxoodyleids.n,

Theoxidationmay be carried outinthepre once 01 solvents preierablywater-miscible solvents suchasthelowerorsanlcacidaas aceticacidoracrylio acld,aloonollorketones.-Itisalsopossibletocarryoutthsoxidationinthe presence or water and asatisiactory method or operation is to use the cataly 8-. Macldlntheiormoilts aqueoussolutionorsuspension. It is possible accordinsto the process oi the present invention to carry the oxidationsubstantially to completion. without undue poly- E e Im- Distillerscompany Limited. Edinburgh, Scotland, a British company No Dre-wins.Application September 20, 1941. 8e-

Brltain September The oxidation is normally carried out at ordinarypressure but. it desirable. increased pressure may be employed.

Instead or recovering the acrylic acid as such. it may be recovered inthe term or its esters. The oxidised reaction mixture may, tor example.be treated with acetylene in the presence 0! suitable catalysts, such asmercuric oxide, and the acrylic acid converted directly into vinylacrylate. Alternatively, the reaction mixture may be treated with analcohol and an esteriflcation catalyst. Yet another method is to causeesteriilcation or the acrylic acid to take place simultaneously with theoxidation by carryinz outihe oxidation in the presence of an alcohol. Itin the latter process the temperature is maintained at a low level. theformation of acrolein aeetal can be substantially avoided.

The process is applicable not only to the oxidation or acrolein but alsoto the oxidation or achloro-acrolein.

The following examples illustrate the manner in which the invention iscarried into eflect in the production of acrylic acid.

Example 1 32 grams or acrolein were dissolved in cc. of acetone and 5cc. or acetic acid. The solution wastbentreatedwithoxyeeninthepresenceoi2 cc. or a 1% aqueous vanadic acid solution at 30' C. After live hours64% of the acrolein wasoxidisedtoacrylicacidwhile3o% remained,

unchanged. No polymerisation was observed.

trample s A mixture containins zrams absolute alcohoLd3lramsacrolein.5cc.aceticacldand 2cc.olai% aduewsvanadicacidsolutionwastreated with oxygen at about 30" C. After a short induction period theabsorption 01 oxysenlncrealed somarkedly that'intensive coollnl voxidatlonunder mueoaniaontastmueiasahcdn cilicm mm-Thersactionploductoontsined 32% acrylic acid and 62% of ethyl acrylate.No polymerisation was observed.

Example 4 The voluminous precipitate obtained by heating sodium-vanadatewith acetic acid was redispersed in acetic acid and added to an aceticacid solution containing 40% by weight of acrolein. This solution wasoxidised at 10 C. by passing in oxygen under a pressure of 1300 mm. Hg.The yield of monomeric acrylic acid was 93.2%, 87.0% of the acroleininitially present having undergone reaction.

Example 5 the water in the catalyst solution is removed. The yield ofmonomeric acrylic acid was 92%.

What we claim is:

1. A process tor the manufacture of acrylic acid comprising treatingacrolein in presence of acetic acid with an oxygen-containing gas in thepresence of a catalyst comprising an aqueous solution of vanadic acid ata temperature not exceeding 45 C. to produce a reaction productcontaining monomeric acrylic acid and peroxidic compounds.

2. A process according to claim 1 wherein the reaction is carried out ata temperature of 20 to 30 C. and in presence of a water-miscible 0r-Banic solvent.

3. A process according to claim 1 wherein the catalyst is prepared insitu by reaction between vanadium pentoxide, acetic acid and hydrogenperoxide.

HANNS PETER STAUDINGER KARL HEINRICH WALTER TUERCK

